1. Field of the Invention
The present invention relates to an air bag for restraining an occupant at a time of collision of an automobile or the like, and to an air bag device utilizing the air bag.
2. Description of the Related Art
The air bag device restrains the occupant by inflating and expanding the air bag from a folded state by ejected gas from an inflator in case of emergency, such as collision and rolling of an automobile. When a vent hole is provided in the air bag, the above described occupant or the like can be softly received with the air bag by flowing out the gas from an internal portion of the air bag via the vent hole when the occupant or the like comes into contact with the inflated air bag.
As a driver seat air bag which is provided in a driver seat and restrains the occupant (driver), among the air bags provided with the vent hole as mentioned above, for example, a prior art described in JP, A, 2008-56175 has been known. The prior art is structured such that the vent hole is closed or is in a small opening degree state, until an internal pressure of the air bag becomes equal to or higher than a predetermined pressure, and the vent hole is opened or in a large opening degree state when the internal pressure of the air bag becomes equal to or higher than the predetermined pressure and the occupant comes into contact with the air bag.
In the air bag, the vent hole is provided at a position closer to an outer peripheral side of the air bag than a steering wheel in an arrangement when the air bag inflates and expanded in a rear panel, and the vent hole is covered with a lid member from an inner side of the air bag. Further, a strap coupling a front panel and the rear panel in an inner portion of the air bag is coupled to the lid member by a tether. Further, on a side closer to the center of the air bag than the vent hole, the tether is pinched between the front panel and the rear panel, and they are connected releasably by a linear sewing part formed by sewing or the like. As a result, when the internal pressure of the air bag becomes equal to or higher than the predetermined pressure, the connection among the front panel, the rear panel and the tether by the linear sewing part is released. Subsequently, the lid member is inhibited from moving to an external portion side of the air bag by the tether so as to overlap the vent hole until the occupant comes into contact with the air bag. As a result, the vent hole is closed or is in the small opening degree. Further, when the occupant comes into contact with the air bag and the front panel moves backward, the lid member gets away from the vent hole due to gas pressure in the internal portion of the air bag. As a result, the vent hole is opened or is in the large opening degree.